Antipope Eulalius (died 423) was antipope from December 418 to April 419, in opposition to Pope Boniface I. At first the claims of Eulalius as the rightful Pope were recognized by the Emperor Honorius, who sent a letter dated 3 January 419 recognizing him and pardoning the partisans of Boniface provided they left Rome.
On 6 January Eulalius celebrated Epiphany at St. Peter's, while Boniface and his supporters remained at St. Paul's-outside-the-Walls.
But Boniface's supporters refused to concede defeat, and petitioned the Emperor, claiming irregularities in the election. In response, Honorius suspended his previous order on 15 January, and summoned both parties to appear before him, along with other Italian bishops, on 8 February. At that hearing, a final judgment was deferred to a second synod that would meet at Spoleto on 13 June. Meanwhile, all parties were ordered to stay out of Rome, and the bishop of Spoleto would celebrate mass on "the greatest of all Christian holy days."
Despite this reversal Eulalius' position appeared to be the stronger, for he had the support of the Empress Galla Placidia and her husband Constantius, because he had been elected first. However, Stewart Oost believes this very strength led Eulalius to overconfidence. He returned to Rome 18 March to celebrate Easter Sunday, but this flouting of the Emperor's orders lost him the support of these two powerful individuals; the inhabitants of Rome rioted, and the Urban prefect, Aurelius Anicius Symmachus, had his police occupy the Lateran, where Eulalius had made his base, and escort Eulalius out of the city to a house and kept under guard. On 3 April, the Emperor officially recognized Boniface as the rightful Pope.
Eulalius is said to have subsequently become a bishop under Celestine I According to the Liber Pontificalis, Eulalius was deposed by a synod of 52 bishops and sent to Campania; then, when Boniface died in 422, the people and clergy of Rome petitioned him to be the new Pope, but Eulalius refused their offer. The same source states he died one year later.